This disclosure relates to evaluating geological formations and, more particularly, to the determination of formation parameters using electromagnetic measurements.
Multi-component directional electromagnetic tools and algorithms have been developed to obtain formation resistivity (e.g., horizontal resistivity—Rh; and vertical resistivity—Rv), anisotropy, and formation dips. In many processing methods, the earth is assumed to be a 1D (1-dimensional) layered mud cake model. 1D processing algorithms can be used for computing electromagnetic induction and propagation responses in 1D layered formation models. Generally, 1D processing provides a fast analytical solution within a reasonable amount of time, and thus inversions based on 1D processing are practical for solving for resistivity, anisotropy, formation dip, and/or layer thicknesses using a 1D layered mud cake model. However, in most real world instances, subsurface formations in the Earth are not a 1D structure, but rather 2D or 3D (non-1D).